While an interesting thought experiment, you need to realize it would take a small army to build something like this – and in Post-whatever Land, you’re gonna need folks with some pretty specialized skills to pull it off. Carpenters, masons, probably a surveyor or two, a genuine Civil Engineer – plus the raw materials to do it… and all these people need to be fed and also protected while the project is underway – and whatever you build will in and of itself be a nice juicy target for anyone who’s bent on making life difficult for you…

Thing is, in Post-land, as roadways become more and more dangerous, waterways might once again become routes of travel – especially for goods. If you outright owned the land on both sides of the water, that might pay dividends, but also presents logistical challenges if you’re at the edge of your tribe’s territory…

Not saying it’s impossible – far as I’m concerned, all it requires is the will and the means to do it. This kind of thing has already been done long ago – nothing to re-invent. The trick is to pull it off with what you’re going to have on hand or can scrounge…

Not trying to squash your enthusiasm – just saying there’s going to be issues that will crop up that you haven’t given thought to..

The wicked flee when none pursueth..." - Proverbs 28:1